1. Field of the Invention
The present invention relates to a cutter mechanism for cutting a recording sheet while sandwiching the recording sheet by sliding a movable blade with respect to a fixed blade, and relates to a printer with a cutter having the cutter mechanism.
2. Description of the Related Art
In recent years, a number of various kinds of thermal printers have been provided, which perform printing by pressing a thermal head against a special recording sheet (heat-sensitive sheet) that develops color when applying heat to the sheet. In particular, the thermal printers enable smooth character printing and colorful graphic printing without using toner, ink, etc., and hence the thermal printers are used preferably for printing of various labels, sales checks, tickets, and the like.
As typified by the thermal printers, a number of printers with a cutter having a cutter mechanism for cutting a printed recording sheet are known. The cutter mechanism generally includes a fixed blade and a movable blade capable of being slid with respect to the fixed blade. When cutting a recording sheet, the cutter mechanism slides the movable blade so that the movable blade rides on an upper surface of the fixed blade. Thus, the cutter mechanism can cut the recording sheet while sandwiching the recording sheet between both the blades like scissors.
In general, the fixed blade is held so that a cutting edge side swings up and down, and is biased so that a cutting edge is pressed against the movable blade by biasing means such as coil springs. Therefore, when the movable blade is slid, both the blades come into contact with each other under an appropriate contacting pressure. Thus, the blades are designed so as to be capable of cutting a recording sheet finely.
The movable blade is formed in a substantially V-shape when viewed from above and is designed so as to come into contact with the fixed blade at two right and left points when riding on the fixed blade. Therefore, along with the slide of the movable blade, the two right and left contact points move along the cutting edge of the fixed blade from both sides of the recording sheet to the center thereof. Thus, the recording sheet can be cut satisfactorily from both right and left sides of the recording sheet without a bias.
Incidentally, in order to cut a recording sheet satisfactorily from both right and left sides of the recording sheet to the center thereof, it is considered to be important that the movable blade and the fixed blade are held in press-contact with each other equally at two right and left contact points. A difference in press-contact may increase a risk that various cutting defects such as uncut portions and wrong shapes of cut surfaces are caused.
In this context, a printer is known in which a fixed blade is pressed against a movable blade by coil springs, two protrusion parts protrude from a root portion side (opposite side of a cutting edge) of the fixed blade, and the fixed blade is held while the protrusion parts are inserted in slot parts of a fixed blade holding member (see Japanese Patent Application Laid-open No. 2005-271204).
According to the above-mentioned printer, the cutting edge of the fixed blade and the cutting edge of the movable blade are allowed to be held in press-contact with each other under an appropriate contacting pressure, which enables a recording sheet to be cut finely.
In particular, the slot part is formed to have a size larger than that of the protrusion part so that a play space (looseness) is secured between the inserted protrusion part and the slot part. Therefore, the fixed blade can swing slightly in a blade width direction due to the play space. Thus, even if there is a difference in a press-contact force between two right and left contact points when the movable blade is slid, the blades are designed so that the fixed blade swings in the blade width direction to render the press-contact force equal easily.
However, in the above-mentioned conventional printer, the fixed blade is designed so that a cutting edge side swings up and down. Further, one of the movable blade and the fixed blade is generally warped to be curved in the blade width direction in order to bring both the blades into contact with each other reliably at two right and left points.
Thus, when the movable blade is slid so as to ride on the upper surface of the fixed blade when cutting a recording sheet, as illustrated in FIG. 25, a fixed blade 201 pushed up by biasing means 200 is pushed by a movable blade 202 to lie down along with the proceeding of the slide of the movable blade 202, and a cutting angle θ becomes small gradually. That is, a cutting angle θ2 at a cutting end becomes smaller than a cutting angle θ1 at a cutting start, and cutting defects such as uncut portions are likely to occur in the recording sheet in the vicinity of the cutting end.
Further, in the above-mentioned conventional printer, the fixed blade can be swung in the blade width direction, using the play space secured between the protrusion part and the slot part. However, the fixed blade can be swung merely within the play space, and it is also difficult to make the most of each play space because two protrusion parts are formed.
Accordingly, a swing amount is limited, which makes it difficult to expect a high swinging property. Therefore, cutting defects are likely to occur also in this respect.